Abstract—Rapid administration (0·4 ml in 1 sec) of the convulsant inhalant, flurothyl (hexafluorodiethyl ether, indoklon), to mice induced within 10 sec clonic‐tonic seizures that were accompanied by marked decrease of P‐creatine, decrease of ATP and glucose, and increase of lactate in the cerebral cortex. In contrast, mice to which flurothyl had been administered slowly (0·05 ml every 30 sec for 10 min) exhibited myoclonic jerks after about 3 min, merging into irregular clonus at about 5 min, and intermittent clonus thereafter until onset of tonic hind limb extension at about 10 min. In these mice, P‐creatine in cerebral cortex decreased gradually for 6 min and then remained through 10 min at levels nearly as low as those reached 10 sec after rapidly administered flurothyl. Lactate in cerebral cortex increased much more during the 10 min of slow administration of flurothyl than in 10 sec of rapid administration, the greatest increase occurring at 4–6 min, as myoclonic jerks merged into irregular clonus. Glucose and ATP in cerebral cortex fluctuated somewhat but did not decrease greatly when flurothyl was administ